8 weeks is generally good, but if you can keep the kittens until they are old enough to spay/neuter, it would be better to make sure they that is taken care of before adopting them away. Some vets can do this as early as 12 weeks, depending on their technique.

Once your kittens are weaned (usually by 6-8 weeks) from their mother they will be ready to find new slaves to own and control for the rest of their purring lives. Do not try to wean them too early as causes issues medically for them in their lives.